Logitech Trackman Marble Mouse

The “Logitech Trackman Marble Mouse” is probably the best trackball on the market now, under $30. The ball is not the largest, but largish, and it spins well. It got 4 buttons. Got excellent reviews, and pretty cheap. Missing a scroll wheel would probably be the only flaw.

From a physical operative mechanism point of view, the concept of trackball pretty much includes the functionality of scroll wheel. Holding one of the button, then the ball functions as a scroll wheel.